Pulsed Electric Field

The effect of thermosonication (TS) and pulsed electric fields (PEF) on inactivation of Staphylococcus aureus (SST 2.4) and selected quality aspects in orange juice was investigated. Conventional pasteurization (HTST, 94 °C for 26 s) was used as a control. TS (10 min at 55 °C) applied in combination with PEF (40 kV/cm for 150 micro-s) resulted in a comparable inactivation of S. aureus to that achieved by conventional HTST. TS/PEF did not affect the pH, conductivity, or °Brix and had a milder impact on the juice color than thermal treatment. Furthermore, the non-enzymatic browning index was significantly affected by HTST (P < 0.05) but not by TS and PEF. Ascorbic acid retention was almost complete after TS and PEF (96.0%), but it was substantially lower (P < 0.05) after HTST (80.5%). Residual activity of pectin methyl esterase (PME) decreased as PEF field strength and treatment time increased; however, applying TS and PEF in combination left a greater residual PME activity than HTST (12.9 vs 5.0%, respectively).

This study aimed to apply Pulsed Electric Field (PEF) for Chlorella vulgaris TISTR8580 intracellular extraction. Twenty-five g/L of algal cell samples were treated with PEF at 5 kV/cm under different pulses (1,500
2,500 3,500 and 4,500 pulses) with the initial temperature of 7 degree Celsius. Temperature, pH and conductivity were measured before and after treatments. Total carbohydrate and protein contents in the crude extracts were determined by the Phenol sulfuric acid method and the Bradford assay, respectively. Subsequently, carbohydrate
composition was analyzed by Thin Layer Chromatography (TLC). In addition, the morphology of PEF-treated cells was observed under light microscope and cell survival was examined by re-culture in BG-11. The results showed an increased number of PEF pulses raised the temperature and conductivity of the algal extract. The highest total carbohydrate (23.19 ± 1.47 mg/L) and protein (144.48 ± 1.41 g/L) contents were obtained from the crude extract treated with 2,500 pulses. TLC revealed that disaccharides and oligosaccharides were the major carbohydrate composition in the extract. PEF-treated algal cells exhibited color fading without any cell lysis. However, PEF
treatment at 2,500 pulses led to cell death. This study clearly suggested that PEF is a potential technology for C. vulgaris TISTR8580 carbohydrate and protein extraction. Further optimization to enhance PEF extraction efficiency are still needed to achieve high yield of algal intracellular extract.

The objective of this review has been to disclose collected information on benefits and risks of selected “less-than – sterilizing” processes applied to control microbial hazards in food that was meticulously collected and critically reviewed during five years of EU Sixth framework project “Pathogen Combat”. The target organisms of the project, and thus of this review, too, were Listeria monocytogenes, Escherichia coli O157:H7 and Campylobacter jejuni. Due to their specific response and high relevancy to the food safety, foodborne viruses and spores, were also discussed within the scope of this review. Selected treatments comprised High Pressure Processing, Intense Light Pulses, treatments with organic acids, treatments with chlorine dioxide and for their relevancy also mild heat treatments and Pulsed Electric Field processing were included. The main aspects included in this review were principles of the processes used and their application, sub-lethal injury and its consequences on microbial food safety, and legal platform and its impact on wide use of the treatments. Finally a reflection has been made to combined application of different hurdles and accompanying risks.

Thermosonication (TS) and pulsed electric fields (PEF) represent emerging technologies for liquid food preservation.
In the present study shelf life and sensory attributes of orange juice were evaluated following treatment with a combination
of these technologies (TS/PEF). The juice was exposed to batch TS at 55 °C for 10 min followed by continuous
PEF at a field strength of 40 kV/cm for 150 micro-s. High-temperature short-time (HTST) pasteurisation (94 °C for 26 s) was
used as a control. Sensory attributes (i.e. colour, odour, sweetness, acidity, flavour and overall acceptability) of different
orange juices processed with TS/PEF or exposed to HTST pasteurisation were evaluated by 37 panellists using a
hedonic scale (1.9 points). All sensory attributes were rated equivalent for TS/PEF- and HTST-treated juice (P>=0.05).
During the shelf life study the effect of TS/PEF on selected physical properties (pH, °Brix and conductivity), microbiological
activity and colour stabilitywas monitored directly after processing and following 25 °C storage up to 168 days.
No significant change in the physical propertieswas detected after TS/PEF or HTST treatment during 168 days of shelf
life (P>=0.05). Although the counts for both treatments were consistently within safe levels (<1000 CFU/ml) during the
168 days of storage, overall microbial counts in TS/PEF-treated juice were higher than in thermally pasteurised juice
(P < 0.05). Colour attributes showed significant differences between TS/PEF- and HTST-pasteurised juice throughout
the shelf life study (P < 0.05). Although promising results have been obtained further optimisation is required in order
to maximise the quality of the resulting product.

Intense nanosecond pulsed electric fields (nsPEFs) have been shown to induce, on intracellular structures, interesting effects dependent on electrical exposure conditions (pulse length and amplitude, repetition frequency and number of pulses), which are known in the literature as “bioelectrical effects” (Schoenbach et al., IEEE Trans Plasma Sci 30:293–300, 2002). In particular, pulses with a shorter width than the plasma membrane charging time constant (about 100 ns for mammalian cells) can penetrate the cell and trigger effects such as permeabilization of intracellular membranes, release of Ca2+ and apoptosis induction. Moreover, the observed effects have led to exploration of medical applications, like the treatment of melanoma tumors (Nuccitelli et al., Biochem Biophys Res Commun 343:351–360, 2006). Pulsed electric fields allowing such effects usually range from several tens to a few hundred nanoseconds in duration and from a few to several tens of megavolts per meter in amplitude (Schoenbach et al., IEEE Trans Diel Elec Insul 14:1088–1109, 2007); however, the biological effects of subnanosecond pulses have been also investigated (Schoenbach et al., IEEE Trans Plasma Sci 36:414–422, 2008). The use of such a large variety of pulse parameters suggests that highly flexible pulse-generating systems, able to deliver wide ranges of pulse durations and amplitudes, are strongly required in order to explore effects and applications related to different exposure conditions. The Blumlein pulse-forming network is an often-employed circuit topology for the generation of high-voltage electric pulses with fixed pulse duration. An innovative modification to the Blumlein circuit has been recently devised which allows generation of pulses with variable amplitude, duration and polarity. Two different modified Blumlein pulse-generating systems are presented in this article, the first based on a coaxial cable configuration, matching microscopic slides as a pulse-delivery system, and the other based on microstrip transmission lines and designed to match cuvettes for the exposure of cell suspensions.

Smoothie-type beverages are usually preserved by mild pasteurisation (MP) but combining moderate heat (H) and pulsed electric fields (PEF) could represent an alternative technique achieving similar, or better, microbiological safety and shelf life, and possibly lowering the thermal impact on physical and sensory product properties. Following H (55 °C after 60 s) and PEF (34 kV/cm, 60 micro-s) the microbiological shelf life of smoothie stored at 4 degrees C was extended over that of mildly pasteurised (72 °C, 15 s) smoothie (21 vs. 14 days (P < 0.05), respectively). Similar trends were obtained for both treatments regarding the shelf life stability of smoothie pH and conductivity (P >= 0.05). H/PEF-treated smoothie achieved better stability of Brix and viscosity than MP (P < 0.05) while better colour stability was obtained for the latter than for H/PEF-treated smoothie (P < 0.05). Sensory evaluation of untreated, MP-treated and H/PEF-treated smoothie indicated comparable overall acceptability of the products (P >= 0.05). Due to superior microbiological shelf stability and generally comparable attributes of the smoothie-type beverage H/PEF preservation proved to be a feasible processing alternative to fruit smoothie treatment with MP.

This research paper mainly solves the problem of the independent driving and coordinated control between the four-wheel hub motors in electric vehicle. In order to drive four motors independently it is required to set the correct speeds when the vehicle takes a turn. This research paper gives and control algorithm and a motor controller model to set the ratio of wheel speeds of inner and outer wheels to make a smooth turn while maintaining the desired speed of linear motion.